This invention relates to a process for the preparation of ethynylbenzaldehydes. In a further embodiment, the invention also relates to selected, novel intermediates formed in carrying out the process herein.
At least two processes for the preparation of the subject compounds have been disclosed in the prior art. In one such process described by K. S. Lau et al. in J. Polymer Sci., Polymer Chem. Ed. 21, 3009 (1983) and also by W. B. Austin et al. in J. Org. Chem. 46, 2280 (1981), a silane protected acetylene is reacted with 3-bromobenzaldehyde to form a protected intermediate which thereafter is cleaved to generate the desired 3-ethynylbenzaldehyde. Yields of 80% are reported. The main disadvantage of this two-step process lies in the use of a relatively expensive starting compound, ethynyltrimethyl silane, which makes the process too expensive for commercial use. Another process, described by J. Ojima et al. in Chem. Lett. (7), 633 (1972), also reported in CA Vol 77, 126305 m (1972), utilizes a time-consuming, multi-step process which suffers from low yields.
There is a need in the art for a process for preparing the subject compounds in high yields, utilizing relatively inexpensive starting compounds and reagents.